Polychlorinated biphenyls (PCBs) and DDT are toxic, widespread hydrocarbons that are poorly understood in terms of their toxicity for human beings. Both of these chemicals pass from mother to child across the placenta and through breast milk. This project includes three studies of subjects exposed to either low levels of these compounds in the U.S. or to higher doses in Taiwan. Two studies are of children and one is on adults. The Breast Milk and Formula study is a birth cohort follow-up study of 856 North Carolina children. PCBs and DDE (the stored metabolite of DDT) are measured in breast milk and the children are followed medically over time. Most of the children have completed 5 years of observation and are now followed only by a birthday card registry. An early finding from the study is that women with higher levels of DDE breast feed for shorter lengths of time. Levels of DDE are higher in countries with active spraying programs. An epidemic of 2000 cases of PCB poisoning occurred in Taiwan in 1979. Rice oil was accidentally contaminated during manufacture. We did a survey of 108 children who were born to mothers who were poisoned, 40 of their older siblings, and 106 controls. All children received a physical examination and the mothers answered a questionnaire about their children's health. Another study of this outbreak will use a modification of an assay for sister chromatid exchanges to evaluate subtle genetic damage and also investigate the immunologic changes associated with exposure to the contaminated oil.